1. Field
The exemplary embodiments generally relate to an apparatus and method for encoding/decoding pictures (including images and videos) to provide high-quality services in various network and device environments, and more particularly, to a multilayer (or hierarchical) picture encoding/decoding apparatus and method for reducing a dynamic range of residual pictures occurring in enhancement layers.
2. Description of the Related Art
Multilayer picture encoding/decoding has been provided to satisfy Quality-of-Service (QoS) determined by various bandwidths of the network, various coding capabilities of devices, and user's control. To this end, an encoder generates multilayer picture bitstreams by one encoding, and a decoder decodes the multilayer picture bitstreams according to its decoding capabilities. Spatial, temporal and Signal-to-Noise Ratio (SNR) layer encoding may be achieved by this multilayer picture encoding/decoding, and depending on application scenarios, N-layer encoding/decoding (where N≧2) is also possible. For example, a base layer may encode pictures having a basic resolution, a first enhancement layer may perform additional encoding to obtain pictures having a higher resolution, and a second enhancement layer (higher than the first enhancement layer) may also perform additional encoding to obtain pictures having a much higher resolution.
When using lower layer pictures in an enhancement (or higher) layer encoding/decoding process, the conventional multilayer picture encoding/decoding apparatus copies lower layer pictures if enhancement layer pictures are equal to lower layer pictures in resolution, and performs up-sampling/conversion on lower layer pictures if the enhancement layer pictures are different from the lower layer pictures in resolution. If enhancement layers use lower layer pictures in this way, picture prediction efficiency may be reduced in the enhancement layers when encoding effects such as quantization errors are reflected intact in the lower layer pictures. Therefore, a scheme for reducing a dynamic range of residual pictures is required.